Production of transforming growth factor alpha by hamster eosinophils

Abstract

Previously it was demonstrated that malignant transformation of the Syrian hamster cheek pouch mucosa is associated with the expression of TGF-alpha. Therefore in situ hybridization and immunohistochemistry was used to investigate the cellular sources of TGF-alpha production in this model system. Surprisingly one cell type in the inflammatory infiltrate present in the connective tissue adjacent to the transformed epithelium represented a major source of TGF-alpha mRNA. Detailed analysis of these cells revealed that they were eosinophils. In addition to TGF-alpha mRNA, about 40% of the eosinophils associated with the oral tumors exhibited TGF-alpha product reactive with a monoclonal antibody against the C terminus of the mature TGF-alpha peptide. Normal hamster bone marrow eosinophils also exhibited TGF-alpha mRNA and product by in situ hybridization and immunohistochemistry. These results suggest that the eosinophil represents a biologically significant source of TGF-alpha.